Can views be created in PL/SQL Functions? - sql

Question

I'm at the beginning of learning PL/SQL. My question is can views be created inside a function?
CREATE OR REPLACE FUNCTION most_sold_item(in_year INT)
RETURN INT
IS
most_shipped_item INT := 0;
BEGIN
CREATE OR REPLACE VIEW Shipped_Items AS
SELECT ITEM_ID,SUM(QUANTITY) AS Total_Quantity
FROM ORDERS, ORDER_ITEMS
WHERE Orders.Order_ID =Order_Items.Order_ID
AND Status=1
AND Order_Year=in_year
GROUP BY Item_ID;
SELECT Item_ID
INTO most_shipped_item
FROM Shipped_Items
WHERE Total_quantity=(
SELECT MAX(Total_Quantity)
FROM Shipped_Items);
return most_shipped_item;
END;
/
Here's my code. There seems to be some kind of error which I just can't find. Can anyone please help me with this?
Thank you.
Here's the snippet of the datatbase that I'm working on

Answer 1

Here's a rough idea of what you might do, if you wish to use a function for this (Added logic to break ties):
-- Estimated structure based on posted image:
CREATE TABLE orders (
order_id int primary key
, client_id int
, order_year int
, status int
);
CREATE TABLE order_items (
order_id int
, item_id int
, quantity int
, ppu int
, primary key (order_id, item_id)
);
-- The adjusted function:
CREATE OR REPLACE FUNCTION most_sold_item(in_year INT)
RETURN INT
IS
most_shipped_item INT := 0;
BEGIN
WITH shipped_items AS (
SELECT ITEM_ID, SUM(QUANTITY) AS Total_Quantity
FROM ORDERS, ORDER_ITEMS
WHERE Orders.Order_ID =Order_Items.Order_ID
AND Status=1
AND Order_Year=in_year
GROUP BY Item_ID
)
SELECT Item_ID
INTO most_shipped_item
FROM Shipped_Items
WHERE Total_quantity=(
SELECT MAX(Total_Quantity)
FROM Shipped_Items
)
ORDER BY item_id
FETCH FIRST 1 ROW ONLY
;
return most_shipped_item;
END;
/
Don't forget to protect for the case where more than one item_id matches the MAX. That's easy to do, but I don't know how you wish to handle that case. I've adjusted the above solution to protect against this issue.
The question edit queue is full. Here's an executable test case (without data) that could be added to the question:
Executable test case, derived from the posted image (without data)

Answer 2

To answer your "original" question:
Can views be created in PL/SQL Functions?
Yes, they can. Should you do it? Definitely not, that's not how Oracle works (in most cases). In Oracle, we create objects at SQL level and use them in SQL or PL/SQL, but we do not create them from PL/SQL.
Anyway, here you are; read comments within code. I used Scott's sample schema as I don't have your tables, but the principle remains the same.
Function:
SQL> create or replace function f_test(par_deptno in number)
2 return number
3 is
4 -- you can't perform DDL in PL/SQL procedures unless they are
5 -- autonomous transactions
6 pragma autonomous_transaction;
7 retval number;
8 begin
9 -- you can't perform DML in a function unless you use dynamic SQL
10 execute immediate
11 'create or replace view v_emp as ' ||
12 ' select ename, sal ' ||
13 ' from emp ' ||
14 ' where deptno = ' || dbms_assert.enquote_literal(par_deptno);
15
16 -- you can't use an ordinary SELECT statement because at time of
17 -- procedure compilation view V_EMP doesn't exist yet, so compile
18 -- would fail
19 execute immediate
20 'select sum(sal) from v_emp ' into retval;
21
22 return retval;
23 end;
24 /
Function created.
Testing:
SQL> select f_test (20) from dual;
F_TEST(20)
----------
10875
What does the view contain?
SQL> select * from v_emp;
ENAME SAL
---------- ----------
SMITH 800
JONES 2975
SCOTT 3000
ADAMS 1100
FORD 3000
SQL>